The invention relates to a method for detecting cornering, specially for a vehicle having an automatic transmission, in which the rotational speed signals are taken up on the wheels of the vehicle and a control device cyclically determines a current bend radius.
Such methods are used in already known transmission controls, for example, to detect, depending on the actual transverse acceleration of the vehicle, a xe2x80x9ccorneringxe2x80x9d mode and to stifle gear shifts. DE 196 18 805 A1 has disclosed a method for evaluating a cornering in an automatic transmission in which rotational speeds measured by a measuring device on the wheels of the vehicle are used to calculate a transverse acceleration of the vehicle.
In long vehicles such as semi-trailers the known methods are not well suited to determine the beginning of a curve and the end of a curve. A tractor, for example, can already drive straight ahead again while the semi-trailer is still in a curve.
Therefore, this invention is based on the problem of providing a simple reliable method for long vehicles a quick detection of xe2x80x9ccorneringxe2x80x9d.
According to the invention the beginning of a cornering mode is determined when the bend radius calculated form the rotational speed signals of the front wheels falls below a first limit radius. The rotational speeds of the front wheels are used in order to detect as early as possible a cornering mode. After exceeding a second limit radius, the end of the cornering mode is only determined when a certain distance related to the length of the vehicle is covered while the first limit radius is no longer fallen below. Therefore, in the example of the semi-trailer, the end of the cornering mode is not detected when the tractor again moves straight ahead but only after a certain distance has been covered while the semi-trailer still moves around the curve.
The second limit radius is advantageously larger by a presettable amount than the first limit radius. This radius hysteresis prevents a reciprocal jumping between the modes xe2x80x9ccorneringxe2x80x9d and xe2x80x9cstraight ahead drivingxe2x80x9d.
In an advantageous development of the inventive method the limit radii depend on the vehicle speed stored in the transmission control, the limit values at low speeds of the vehicle being smaller than at high speeds of the vehicle. Hereby is prevented that numerical inaccuracies, the consequences of which are great at low speeds of the vehicle, result in that a cornering mode be erroneously determined.
The consequences of individual inaccurate measurements can be reduced by upwardly limiting by a maximum admissible change the change of the calculated bend radius between two consecutive scanning steps.
The signal of he calculated bend radius can be advantageously stabilized by a PT1 filter element.
Wheel slip on individual wheels could lead to malinterpretations of the bend radius for which reason it is advantageous not to determine a cornering mode when a wheel slip prevention system such as ABS or ASR is active. It is also advantageous to preset a minimum speed below which a cornering is not determined in order to prevent malinterpretations due to numerical inaccuracies.
The inventive method and developments thereof can advantageously be used to control an automatic transmission wherein the triggering from upshifts to downshifts during cornering is influenced. Undesired upshifts and downshifts can thus be prevented when cornering.
The method can also be advantageously used within an algorithm for tractional resistance calculation of the vehicle in order to take into account the tractional resistance increased during cornering. The tractional resistance calculation can be initialized again after the end of the curve.